Electrolysis cell



Dec. 10, 1940. K. PAUL ELECTROLYSIS CELL 2 Sheets-Sheet 1 Filed April19, 1937 125%.:Eiug

INVENTOR.

' KARL PAUL ATiORNEY.

Dec. 10, 1940. PAUL ELECTROLYSIS can Filed April 19.11937 2 Sheets-Sheet2 IN VEN TOR. KARL PA UL iTTbRNEY.

Patented Dec. 10, 1940 UNITED STATES PATENT OFFICE 2,224,831nrnc'raonrsrs can.

Application April 19, 1937, Serial No. 13'lfl19 Claims.

This invention relates to an improved electrolysis cell and to a processemploying that cell in the electrical synthesis oi chemical compounds.Electrolysis cells are well known in the 5 art and may be defined aselectrolytic cells which are used for the synthesis of chemicalcompounds by utilizing the chemical effects of the electric current.

This invention relates more particularly to a new and improvedelectrolysis cell which is particularly adapted for the manufacture ofpersulphuric acid or persulphates by electrolytic synthesis, as well asthe process of utilizing this novel cell for the manufacture of thesechemil 5 cal compounds. Cells for the preparation of persulphuric acidand persulphates by electrolytic synthesis are now used commercially inthe manufacture of hydrogen peroxide. In processes of manufacturinghydrogen peroxide by the electrolytic route, it, is usual to subject toanodic electrolysis a solution of sulphuric acid or an acid solution ofammonium sulphate. In present methods, thesulphuric acid or sulphatesalt is converted into persulphuric acid or persulphate by electrolysiscarried out successivelyin a series of electrolysis cells. After thepersulphuric or persulphate content has been built up to a valuesufllciently high to permiteconomical recovery of hydrogen'peroxidetherefrom, as a result of these successive electrolyses, the solution issubjected to hydrolysis and distillation in order to convert the percompound into hydrogen peroxide and to recover the evolved peroxide fromthe solution.

As the class of electrolysis cell for preparing persulphuric acid orpersulphates by electrical synthesis is well-known in the art, it is tobe understood that wherever hereinafter reference is made topersulphuric acid cells, it is my intention that cells for themanufacture of persulphates by electrolytic methods are to be alsocomprehended within the scope of that term.

It has been usual to utilize in electrolytic processes for theproduction of persulphuric acid an aqueous solution of sulphuric acid,the electrolysis being carried out in a cell having an anode of platinumand a cathode of lead or graphite. It has been .usual to provide twoliquids in these cells, the liquids being independently circulated fromone cell to another throughout the series of cells in which theplurality of separate electrolytic synthesis is carried out. One of theliquids in the cells now known to the art is termed an anolyte and itordinarily is positioned closely adjacent to the anode. The secondliquid is the catholyte, which catholyte is closely adjacent to thecathode. The chambers surrounding the cathode and anode, or the cathodeand anode chambers, are usually separated in electrolysis 5 cells of thetype specified as now known in the art by a porous diaphragm. Thisporous diaphragm separates anolyte and catholyte. liquids and permitsonly the passage of electrical ions therethrough. The diaphragm does notpermit any appreciable diffusion of the two liquids from 10 anodecompartment to cathode compartment. A type of cell now known to the artand utilized commercially in the preparation of persulphuric acid andpersulphates is shown in the Baum Patents 1,837,177 and 1,937,621. Theanolyte, porous diaphragm, catholyte and cathode of this cell are alldisposed concentrically within the cell container.

The group of cells in which the sulphuric acid starting material, oracidic solution of a sulphate, 20 is converted by electrolytic synthesisinto persulphuric acid or persulphates is arranged in present commercialinstallations in such a way that the individual cells constitute what isusually termed a cascade." This means that the 25 anolyte and catholyteliquids leaving one of the cells of the series flow to the next lowercell of the series, in an arrangement which is analogous to a cascade.The concentration of persulphuric acid (or persulphate) in the anolyteis built up 30 to a certain extent by electrolysis in each cell. Theanolyte liquid containing the persulphuric acid formed as the result ofthe electrolysis in one cell is carried over the the next cell of thecascade arrangement wherein the persulphuric 35 acid content is built upby electrolysis to a fur ther'extent. The electrolytic process isrepeated in plurality of cells until an anolytehaving a suflicientlyhigh percentage of persulphuric-acid (or persulphate) to permiteconomical hydrolysis 40 and distillation is obtained. A

I It should be understood that during the proc ess of electrolyticsynthesis both catholyte and anolyte liquids are circulated through theplu- 45 rality of cells forming the cascade arrangement. The catholyteand anolyte liquids are separated by means of a porous diaphragm. If theanolyte were permitted to come in contact with the cathode, persulphuricacid or persulphate pres- 50 cut therein would be destroyed. The processof producing these per compounds electrolytically by the methods nowknown to the art involves building up the concentration of the desiredproduct successively in small incrementsby car- Wing out successiveelectrolyses in a plurality of electrolysis cells.

This porous diaphragm in present cells is designed to prevent diffusionof one liquid into the other by fluid movement therethrough. However, itdoes not prevent the passage 01' electrical ions therethrough, which is,of course, essential in the electrolytic process. As the llquids arekept separate in the cells 'now known to the art during the entireperiod of successive electrolysis in a plurality of cells, both anolyteand catholyte liquids being circulated, the cells now utilizedcommercially for the manufacture of persulphuric acid and persulphates,such as those shown in the Baum patents, are known asdouble-electrolyte, double-flow cells. The electrical input of any oneof these cells is relatively small and the amount of persulphuric acidsegregating one.porti0n of the electrolyte into an anolyte in a chambersurrounding the anode, and a second portion of the anolyte into acathode in a chamber surrounding the cathode, and maintaining theseliquids separate throughout the entire period of electrolysis, I providebut one electrolyte. This electrolyte is permitted to flow both throughthe chambers surrounding the cathode and through the chamberssurrounding the anode.

Instead of securing at the end of the electrolysis two liquids, one theanolyte containing the valuable constituent (persulphuric acidorpersulphate), and the other a catholyte of no value insofar as desiredchemical product is concerned, I secure but one liquid, an electrolyteof substantial persulphuric acid concentration which may be subjected tothe usual hydrolysis and distillation steps in order to secure hydrogenperoxide. The improved cell with which this invention is concerned maybe provided with a porous diaphragm but this porous diaphragm does notcompletely segregate the electrolyte into two portions as in theelectrolysis cells now known to the art.

There is an opening provided in this porous diaphragm which permits flowof electrolyte from the chamber adjacent to onev electrode to thechamber adjacent to the other. In other words, the electrolyte flowsfrom the cathode chamber through the opening in the porous diaphragminto the anode chamber, and from there is carried directly to the stillswherein the hydrolysis and distillation for the recovery of hydrogenperoxide is carried out, This single-pass feature of my improved cell isa marked departure from all electrolysis cells for the manufacture ofpersulphuric acid or persulphate now known or used for the commercialsynthesis of these products.

As previously pointed out, it has been usual in the commercialmanufacture of these per compounds to build up the contentof percompounds successively by subjecting the anolyte (and catholyte) tosuccessive electrolyses in a large number of individual cells. In anarrangement such as that disclosed in the Baum patents, some of thesecells may be arranged at a level lower than other cells so that bothanolyte and catholyte liquids may flow by gravity from one group ofcells to a lower cell in the so-called cascade arrangement. An importantcharacteristic of my new and improved cell is that the persulphuric acidor persulphate content is built up to a much greater degree in onesingle individual cell than ever before attainable by single cellelectrolysis. In other words, the improved cell with which thisinvention is concerned may be constructed of greater size than any nowknown to the art and of greater electrical capacity. My improved cell isdesigned primarily to build up the persulphuric acid content to asufficiently high degree in a single cell, thus eliminating theobjectionable cascade arrangement and successive electrolyses in aplurality of cells, previously considered essential in the manufactureof these compounds. The electrical current applied to any one cellconstructed in accordance with my invention is ordinarily many timesthat supplied to any single cell of the type disclosed in the Baumpatents.

Among the objects of this invention may therefore be enumerated thedevelopment of a singlepass, single-flow cell wherein but oneelectrolyte is subjected to electrolysis, this electrolyte beingnormally built up to a sufficiently high persulphuric acid orpersulphate concentration in a single cell, without the necessity ofcarrying out a plurality of electrolysis in a series of cells as nownecessary in the commercial production of these compounds. Anotherobject of this invention includes the building of an electrolysis cellof the type specified, which cell may be con-' structed of varioussizes, and which may be designed to take much larger electrical powerinputs than those now known or used in this art. Closely allied withthis latter object is the ancillary objective of reducing the number ofcells necessary to secure a liquid having a concentration ofpersulphuric acid high enough to permit economical recovery of hydrogenperoxide from the great number now employed in plants utilizingelectrolytic methods to a single large sized cell. This objective alsoinvolves a concomitant decrease in the operating expense incident to themanufacture of these per compounds by electrical synthesis.

Other objects of this invention involve the utilization in theconstruction of my single-pass, single-flow cell of certain features ofconstruction which make possible for the first time in this art the useof a single-flow cell for the economical manufacture of persulphuricacid and persulphates. These features include a novel anode assembly, anovel diaphragm construction, a novel cathode assembly and novel meansfor cooling that portion of the electrolyte present in the chamber whichcontains the anode. The various features of my improved cell whichpermit the utilization of but one electrolyte in place of the 'twouniversally used in the prior art, these features including, amongothers, the provision of a space underthe diaphragm and cathode assemblythrough which the electrolyte is permitted to flow from cathode chamberto anode chamber or, defined more broadly, the provision of means in thediaphragm through which the electrolyte is permitted to flow, alsoconstitute novel elements contributing to the success of my improvedconstruction.

It may be stated that all diaphragms now known or utilized inelectrolysis cells for the manufacture of persulphuric acid orpersulphates for the anode chamber 51. Water or some other definitelyseparate the electrolyte into two entirely separate portions. Presentdiaphragms do not permit positive passage of liquid therethrough, theonly relative flow between anolyte and catholyte liquids being thatrelatively negligible amount which may occur as a result of the porosityof the diaphragm and the difference in level between the two liquids. Ascontrasted with present diaphragms, the diaphragm of my improved cell isnot constructed inperforate, but is arranged so that a positive flow ofliquid therethrough from one chamber of the cell to the other mayconstantly and continually take place.

My invention, which also involves other and subsidiary objectives whichwill become apparent during the ensuing description of my preferred celland preferred mode of operation, may best be explained in conjunctionwith the annexed drawings wherein:

Fig. l is a vertical section of the entire cell assembly some partsbeing illustrated in elevation. This view is taken along the line 2-2 ofFig. 2.

Fig. 2 is a plan view of an improved cell constructed in accordance withmy invention, the electrical lead-in wires being omitted from this view.

Fig. 3 is a detail view, in elevation, of the cathode assembly with theelectrical lead-in connections shown in place thereon.

Fig. 4 is a detail of the perforated sheet lead cathode which is shownin Fig. 3 in end elevation.

Fig. 5 is a detail of one form of anode assem-' bly. The clamping meansand lead-in wires by which the electrical connection is made to theanode are also illustrated in this view.

Fig. 6 shows an alternative form of anode assembly. This view alsoillustrates the clamping means and electrical lead-in wire by which theanode is connected to a source of electrical current.

Fig. 7 is a detail of the clamping means by which the electrical lead-inwire may be secured to the anode of Fig. 6.

As will be more fully' apparent from the sectional elevation, Fig. 1, myimproved cell includes a cell container Ii which may be constructed ofwelded steel. This sheet steel box is lined with a lead lining l3.Secured to this lead lining by the use of acid-proof cement is an innerceramic liner 15. This liner may be of porcelain or other ceramicmaterial and should have sufllcient thickness to insure adequateelectrical insulation between the electrolyte and the sheet steel cellcontainer.

The porous diaphragm il divides the interior of the cell container intotwo portions. The larger portion, designated by the numeral l8,constitutes the cathode chamber. The smaller porby the numeral 2|,through which fiow of electrolyte from cathode chamber to anode chambermay take place.

Positioned in the chamber in which the anode is suspended and securelycemented to the insulating inner liner IS with acid-proof cement is alead box 23 which serves as a cooling Jacket cooling fluid is permittedto flow into this cooling jacket through the inlet pipe 25 and outthrough the exit pipe 21 (Fig. 2). In this way that portion of theelectrolyte present in the anode compartment is subjected to coolingduring the process of electrolysis. Although lead is specified as mypreferred material of construction for this cooling jacket. as lead isresistant to the action of sulphuric acid, any other material which willserve to transmit heat and which will also stand up under the severecorrosive conditions encountered in such an electrolysis cell may beutilized with equal success. Among other suitable materials may bementioned glass, tantalum and even in some installations platinum,although the latter is of course far too expensive to permit ofcommercial utilization.

The anode is designated in Fig. 1 by the numeral 23. As the drawingillustrates two possible forms of this anode, that shown in Fig. andthat shown in Figs. 6 and 7, a description of the exact construction ofthis anode may be deferred for the present. It may be stated, however,that in the embodiment disclosed in Fig. 1 the anode is closelypositioned adjacent to the porous diaphragm, II. It is provided at theupper end with a metal clamp 3| by which may be secured the electricallead-in connection 33.

Insofar as this description is concerned, the porous diaphragm l1 may beconsidered simply as a porous plate through which ions bearingelectrical charges can readily pass. It may be constructed of someporous ceramic material or of glass wool. v

The cathode assembly is positioned on a grooved acid-proof, stonewareblock 35 which rests on the insulating inner liner I5. This block isprovided with longitudinal grooves which permit the liquid present inthe cathode chamber to flow from this chamber through the grooves andthrough the passage under this porous diaphragm (designated by thenumeral 2|) into the anode chamber. This block may preferably be made ofacid-proof stoneware but can also be made of any other material such aslead, tantalum, glass or other material which is resistant to theactionof sulphuric acid. It constructed of material which electrically.conducts electricity, it must of course be suitably insulated from thecathode assembly.

The cathode assembly consists of the cathode proper which comprises aperforated lead plate designated by the numeral 31. This plate isprovided with a series of holes or apertures 38. It may be suitablysecured, as by burning, to a lead cooling coil 4| provided with inletand outlet conduits 43 and 45, through which water or some other coolingfluid may be permitted to flow for the purpose of cooling the liquidpresent in the cathode chamber. At the bottom of the cooling coil, andsecured to-and forming a part of the lead plate cathode, is a leadbottom plate 41 which abuts against and rests upon grooved block 35.Although lead is specified as the preferred material for my sheetcathode, it must be under also be utilized. Ordinarily platinum wouldnot be used in view of its relatively great cost.

At the upper endthe sheet lead cathode is provided a clamp 49 similar tothat shown on anode 29. By means of this clamp the electrical connectionbetween the cathode and the source of current is made. The clamp'may besecured to the cathode by welding or in any other suitable manner.

Positioned at one side of cathode compartment I8 is an inlet tube 53which may be formed of glass, ceramic material, lead, tantalum, or anyother suitable resistant material. This inlet tube serves to conveyelectrolyte to the cathode chamber of the cell. If desired, it may beomitted and a solution of sulphuric acid in water, or a solution ofsulphate, which is to be electrolyzed, may be poured directly into thecathode chamber. Ordinarily, the use of an inlet tube 53 is desirable asit prevents splashing of acid.

Exit tube 55 is provided at the upper'level of the cooling Jacket 23 inorder that the electrolyte containing the persulphuric acid orpersulphate product may leave the electrolysis cell. As shown, exit tube55 is brought out through an aperture especially formed for the outflowpipe in the sheet steel case, lead liner, and inner ceramic insulatingliner. The outflow tube 55, which may be formed of metal or ceramicmaterial, must be insulated from the steel container and the lead liner.

The course of flow of electrolyte through the cell will now be evident.The electrolyte which, in the manufacture of persulphuric acid, willconstitute an aqueous solution of sulphuric acid, with or withoutvarious addition agents, is fed into the cell or, more particularly,into the oathode chamber through inlet pipe 53. This electrolyte thenpasses from thechamber surrounding the cathode through the groove in theporous stoneware block 3! and throirgh the opening 1| provided underporous diaphragm I I. From here, flow occurs through the narrowpassageway designated by the numeral 51, this passageway constitutingthe anode chamber. In the anode chamber the electrolyte comes intocontact with anode 29 and is thus subjected to anodic electrolysis.Persulphuric acid (or persulphate) is pro duced in the electrolyte asthe result of the electrolytic synthesis carried out in anode chamber51. With its persulphuric acid content built up to a sufllciently highconcentration, the electrolyte flows out through exit tube 55 to thestills where it is subjected to hydrolysis and distillation to recoverhydrogen peroxide therefrom.

As previously specified, a cooling fluid such as water shouldcontinuously flow through the cooling coils 31. This cooling fluid isintroduced through inlet 43 and flows out through outflow pipe 45. As aresult of this cooling, the electrolyte is maintained at a temperaturebelow about 20C. during its passage through the cathode chamber. Theelectrolyte in the anode chamber I1 is cooled by flowing cooling fluidthrough the lead box 23. In this way the electrolyte is, at all times,maintained at a temperature of 20 C. or less.

The anode assemblies disclosed in Figs. 5, 6 and 7 may now be describedin further detail. The anode construction shown in Fig. is alternativeto the construction shown in Figs. 6 and 7, and either one may beutilized in my improved electrolysis cell. It should be understood, ofcourse, that the size of the anode chamber must be designedtoaccommodate whichever anode assembly is selected.

In the construction shown in Fig. 5 a plurality of vertical tantalumstrips designated by the numeral I are supported from a lead cross-baror cross-strip 63. These tantalum strips, which may be of relativelynarrow width and slight depth, may be secured to the lead cross-bar byTantalum is the material which is most suitable for the supportingframe, as it is relatively strong, inert to acid, readily secured toboth lead and platinum by welding, and is a good conductor ofelectricity without itself acting as the electrode'.

The actual anode members in the construction disclosed in Fig. 5 are theplatinum strips designated by the numeral ll. These strips are arrangedcross-wise of the tantalum vertical supporting strips 6|, to which theyare secured by welding. Asshown, a number of these vertical platinumelectrode elements are supported, one above the other, and extendthroughout the entire width of the anode supporting frame. Suflicientplatinum is required to give the required current density at the anode,but the ,strips need be only of relatively narrow width and slightdepth.

Lead-in wire 33 is secured by clamp 3| which in turn is attached to leadcross-bar 63 in any suitable manncr as by welding. As the lead-in wire,and the means of securing this wire to the lead cross-bar by clampingmeans, are now well known in the art, further description thereof isunnecessary. Any standard and well-known manner of making contactbetween the crossbar I and the source of current may be utilized and theparticular means illustrated forms no essential part of my invention. Itmay be stated that the method of securing the lead-in connections to theelectrodes, involving the use of a clamp, is the same in allconstructions shown in the drawing. 4

The alternative form of anode assembly disclosed in Figs. 6 and 7comprises a pair of lead posts 8|, which are covered with tantalumindicated by numeral 82. To the tantalum covered posts is attached, insome suitable manner, as, .7

by welding, a plurality of tantalum cross-strips 83. The lead postscovered with tantalum, ll, may rest on the bottom of the cell, therebeing provided an insulating block, usually of porcelain (not shown) inorder to provide proper insulation. To the cross-strips 83 there aresecured narrow strips of platinum (designated by the same numeral 83)which constitute the actual electrode. The vertical posts it are tiedtogether by means of a lead cross-bar B5 to which is secured, bywelding, a lead clamp 81. This lead clamp is shown in greater detail inFig. 7. By means of this clamp a bolt 8! may serve to secure theelectrical lead-in connection to the anode assembly. It is obvious thatthe relatively more massive anode construction disclosed in Figs. 6 and7 is capable of-carrying a heavier electrical current than the anodedisclosed in Fig. 5. As in the former construction, however,

the-area of platinum used must be sufliclent to.

above apparatus. Current efliciences obtained monium persulphate processconsists of an acid solution of ammonium sulphate, flows'into the cellthrough the inlet pipe 53. If desired, this pipe may be eliminated, butis preferably in- 6 cluded as it prevents splashing of acid solutions.

The electrolyte builds up in the cathode compartment I8 and flowsthrough the perforations 39 in lead sheet cathode 31 so that it fills upthe entire space comprising the cathode compart-- ment btween thediaphragm l1 and the insulat-.

ing lining It.

From the cathode chamber the electrolyte flows through the grooves inthe grooved bottom plate 35 and through the opening 2| below diaphragmII. If desired, the opening Il may be positioned elsewhere in thediaphragm, but I have found it very much more advantageous to positionit at the bottom of the cell.

After flowing through aperture 2|, the electrolyte flows upwardlythrough anode' chamber 5iv where it comes into contact with electrode 29and is subjected to anodic electrolysis. After the electrolysis iscomplete, the persulphuric acid or persulphate content being built up toa concentration sufliciently high to permit economical hydrolysis anddistillation by treatment in the single cell, the electrolyte flows outthrough outlet 55 where it is delivered to stills for the subsequenttreatment usual in this art. During the 30 entire electrolysis theliquid in the cathode chamber is cooled by means of cooling coil 44 andthe electrolyte in the anode chamber is cooled by means of lead box 23.

The acid recovered after hydrolysis of the persulphuric acid and therecovery of hydrogen peroxide by hydrolysis and distillation may be usedas electrolyte in a successive electrolysis operation. Its specificgravity may be adjusted by the addition of fresh acid or distilled waterso that 40 gravity of preferably 1.3 is attained. Acidconcentrations'other than that equivalent to a gravity of 1.3 may ofcourse also'be used.

As noted above, the current density is an important factor in theelectrolysis. I have found 45 that a cathode current density of about0.06 ampere per square centimeter of cathode surface.

It has been found that the electrolyte may be circulated through thecell at the rate of about 55 one-half liter (500 cc.) of electrolyte perminute. Under these conditions, a current of 1000 amperes is supplied tothe cell and the temperature of the electrolyte is maintained at about14 to 17 0.,

preferably below 20 C. The voltage drop across (it) the cell will beapproximately 5 volts. I have obtained current efllciencies of from 70to' 75% and the persulphuric acid content of the eiiiuent electrolytein-the persulphuric acid process has usually been from 8 to 9%. Itshould be under- 65 stood, of course, that these numerical data aremerely given as illustrative, as my invention also involves the use ofcurrents, current densities, voltage drops, and rates of electrolytefiow other than those specified.

70 Solutions of sulphates can also be employed in my improved process.Thus, I may electrolyze, for example, a solution containing 220 grams ofammonium bi-sulphate and 280 grams of sulphuric acid per liter ofaqueous solution. the

75 temperature being maintained below 20 C., in the I do not wish to belimited wish to be limited to exact rates, temperatures, or'compOsitionsgiven, nor to exact construction of the various elements or membersforming my novel persulphuric or persulphate cell. Various changes mightbe made in the construction described as illustrative and preferred,which would nevertheless still be within the purview of my invention.

It may be stated, moreover, that a great variety of solutions may betreated in my improved cell and these solutions will, in general,contain other materials in addition to sulphuric acid or varioussulfates, such, for example, as addition agents and other substancespresent as media to improve the efliciency of the process.

It is therefore my intention that the scope of the invention is to berestricted only as necessitated by the prior art and appended claims. Inthe claims the term persulphuric acid is intended also to includepersulphates such as ammonium persulphate and potassium persulphate.

I claim:

1. An electrolysis cell for the manufacture of persulfuric acid whichcomprises, in combination, a cell container, a porous diaphragmseparating said cell container into two compartments, which compartmentsare adapted to contain an electrolyte, said porous diaphragm beingprovided with an opening permitting communication between saidcompartments, a cathode positioned within one of said compartments, ananode positioned within the other of said compartments, and coolingmeans positioned within each of said compartments for cooling theelectrolyte during its flow throughthe cell, said cooling means in saidcompartment in. which said anode is positioned being so arrangedadjacent said anode as to provide a relatively narrow path of travel forsaid electrolyte through said compartment between said anode and saidcooling means.

2. An electrolysis cell for the manufacture of persulfuric acid whichcomprises, in combination, a cell container, a longitudinally extendingporous diaphragm positioned within said cell container and separatingsaid cell container into two compartments, which compartments areadapted to retain an electrolyte, said porous diaphragm being providedwith an opening permitting communication between said compartments, acathode positioned within one of said compartments, an anode positionedwithin the other of said compartments, cooling means positioned in saidcompartment containing said cathode'in such a manner as to cool theelectrolyte in said compartment, said cooling means being secured to andforming a part of said cathode,

electrolyte, said porous diaphragm being provided with an {openingpermitting communication between said compartments, an anode positionedwithin one of said compartments, a cathode positioned within the otherof said compartments, electrical lead-in wires for supplying electricalcurrent to said anode and said cathode, cooling means positioned withinsaid compartments for cooling the electrolyte, said cooling meanspositioned in said compartment containing the cathode being rigidlysecured to said cathode in such a manner that the eil'ective area ofsaid cathode is thereby increased. said cooling means positioned in saidcompartment containing said anode being positioned closely adjacent tosaid anode in such a manner that a relatively narrow path of travel isprovided for the electrolyte through said compartment in the spacebetween said cooling means and said anode,

means for introducing fresh electrolyte into the compartment in whichsaid cathode is positioned, and means for removing electrolyte which hasbeen subjected to electrolysis from said compartment in which said anodeis positioned and thence out of the cell. a

4. An electrolysis cell for preparing persulfuric acid which comprises,in combination, a cell container, a porous diaphragm separating saidcell container into a pair of compartments adapted to retain anelectrolyte, said porous diaphragm being provided with an openingpermitting communication between said compartments, an anode positionedwithin one of said compartments, a cathode positioned within the otherof said compartments, electrical lead-in wires for supplying electricalcurrent to said anode and said cathode, and a box-like member positionedin said anodecompartment adjacent said anode and-insuch a manner as toprovide a relatively narrow space for travel of the electrolyte betweensaid box-like member and said anode, said box-like member serving toretain a cooling liquid which cools said electrolyte as it passes incontact with said anode.

5. An electrolysis cell for preparing persuiiuric acid which comprises,in combination, a cell container, a longitudinally extending porousdiaphragm separating said cell container into a pair of compartments,which compartments are adapted to retain an electrolyte, said porousdiaphragm being provided with an opening permitting communicationbetween said compartments, an electrolyte positioned within saidcompartments, an anode positioned within one of said compartments, acathode positioned within the other of said compartments, electricallead-in wires for supplying electrical currents to said anode and saidcathode, means for introducing fresh elec trolyte into the compartmentin which said cathode is positioned, means for removing electrolytewhich has been subjected to electrolysis from said compartmentin whichsaid anode is positioned, and a cooling coil positioned in saidcompartment containing said cathode, said cooling coil being integrallysecured to said cathode, whereby the effective area of said cathode isincreased while said cathode and the electrolyte in said cathodecompartment are subjected to cooling during the electrolysis.

KARL PAUL.

